1. Field of the Invention
The present invention relates to bulk processes for making polymers, and more particularly relates to bulk processes for making maleimide copolymers.
2. Description of the Related Art
Maleimide copolymers, specifically N-phenylmaleimide-styrene-acrylonitrile copolymers are known. Processes for making the maleimide copolymers, have generally been complex, and have encountered difficulties including, for example, oligomer control. Undesirably high levels of oligomers in the final product can result in reduced glass transition temperatures and reduced levels of impact strength. Additionally, such processes have typically encountered some difficulties with compositional drift control, particularly in the suspension and emulsion processes. Additionally, various processes, such as bulk processes which employ continuous stirred tank reactors, have typically resulted in undesirably high levels of residual maleimide monomer, specifically N-phenylmaleimide monomer which can have the undesirable effect of producing product with an undesirably high yellowness index.
Accordingly, there is a desire to provide a process which will produce maleimide copolymers exhibiting enhanced glass transition temperatures, reduced levels of yellowness, and reduced levels of viscosity.